Cheese compositions are prepared from dairy liquids by processes that include treating the liquid with a coagulating or clotting agent. The coagulating agent may be a curding enzyme, an acid, or a suitable bacterial culture, or it may include such a culture. The coagulum or curd that results generally incorporates transformed casein, fats including natural butter fat, and flavorings that arise especially when a bacterial culture is used. The curd is separated from the liquid whey, which contains substances not affected by the coagulation, and which therefore are not incorporated into the coagulum. Whey is thus a byproduct of manufacturing and commercial processes that produce food products such as cheeses. Whey contains soluble substances, such as lactose, and proteins, such as .beta.-lactoglobulin and .alpha.-lactalbumin, with molecular weights of about 18 kDa and about 14 kDa, respectively; other proteins include serum albumin, immunoglobulins, and K casein digestion products. Since large quantities of whey are available from the side streams of the food producing processes mentioned above, it would be desirable to increase utilization of the components of whey in the manufacture of dairy products in order to increase the utilization of the raw milk starting material and thereby enhance overall efficiency. The inability of whey proteins to be retained in the coagulum is an important factor contributing to a lack of efficiency in the production of cheese. Such problems have been recognized for many years.
Several methods have been proposed with the objective of recovering whey proteins in cheese products. Many of them include process steps that, although not emphasized, retain or concentrate lactose as well. For example, whey proteins have been concentrated or dried from whey, and then recombined with cheese (see, e.g., Kosikowski, Cheese and Fermented Foods, 2nd ed., Edwards Brothers, Inc., Ann Arbor, Mich., 1977, pp. 451-458). Unfortunately, in such procedures the recovered whey constituents do not have the appropriate physical and chemical properties conducive to making high quality natural cheeses or process cheeses.
Ernstrom et al. (J. Dairy Science 63:2298-234 (1980)) provide a process in which milk is concentrated to about 20% of the original volume by ultrafiltration and evaporation; the lactose content is modulated by diafiltration. The resulting composition is then inoculated with a cheese starter, which also ferments the remaining lactose, and forms a cheese base. In this process, therefore, the lactose is consumed in fermentation rather than retained in a final cheese product.
Banks et al. (Milchwissenschaft 42:212-215 (1987)) disclose that heating milk at temperatures from 95.degree. C. to 140.degree. C. and then acidifying permits a modest increase in protein content in Cheddar cheese. A bitter off-flavor developed in this process. Law et al. (Milchwissenschaft 49:63-37 (1994)) report that heat treatment of milk prior to cheddaring results in reduction of proteins in whey or in acid filtrates of the milk.
Dybing et al. (J. Dairy Sci. 81:309-317 (1998)) provide a process for incorporating whey protein into cheese curd by concentrating the components, coagulating whey proteins using a variety of agents, and renneting a composition containing the coagulated whey protein and concentrated milk components. It was found, however, that these methods did not succeed in producing whey protein coagula that were recovered as cheese.
Guinee et al. (Int. Dairy Journal 5:543-568 (1995)) recently evaluated the state of the art for incorporating whey protein into cheese. High-heat treatment of milk is reported to impair rennet coagulation, curd syneresis, curd structure and texture, and functional properties such as meltability and stretchability. Guinee et al. discuss physical and chemical factors that may be responsible for these effects. Using heat treatments that denature whey protein in milk compositions, they prepared semi-hard cheeses that result from curding such treated compositions. They found that the curd obtained in this way has high whey protein levels, but also high moisture level, low pH value, poor curd fusion and low yield (fracture) values during ripening.
U.S. Pat. No. 5,714,075 relates a method of processing a waste stream generated in a cheese-making process that includes binding anionic components such as sialyloligosaccharides in the waste stream to an anion exchange resin and eluting the anionic components as lithium salts. The lithium salts of the waste stream anionic components are then recovered as solids.
Whey is the aqueous liquid remaining after cheese curds, containing fat, casein, and other components, are produced from a dairy liquid. The composition of whey typically is about 6% solids, of which about 60-70% is lactose. Lactose is a sugar having relatively limited solubility in water. Nevertheless, as with many other sugars, the rate of crystallization of lactose is very slow, requiring days or weeks, depending on conditions. Under the conditions of low water activity prevalent in cheese products, the crystallizability of lactose tends to be enhanced. Such lactose crystals may require several weeks to appear. Thus, even if lactose were present in a cheese formulation at a concentration representing a supersaturated state, crystal formation could be delayed well into a period of storage during shipment, sale, and storage in the home prior to consumption. The presence of lactose crystals, however, would have a severe adverse effect on the mouthfeel of any cheese product in which they might appear, and would deter the consumer from purchasing a product known to engender such crystals.
U.S. Pat. No. 4,048,346 discloses a method of stabilizing a concentrated lactose mixture obtained, for example, from cheese whey by adding to the mixture certain lignin sulfonates in an amount sufficient to retard crystal growth of the lactose. The concentration of lactose is from about 20% to about 35% by weight. The invention also relates to an animal food supplement including a concentrated whey and an amount of certain lignin sulfonates sufficient to retard crystal growth of lactose in the concentrated whey.
U.S. Pat. No. 4,955,363 discloses a method of recovering crystalline lactose from whey. The whey is concentrated, and part of the lactose is crystallized and isolated. The mother liquor is then purified by heating it to about 60.degree. C. to 70.degree. C. at a pH of about 5.8 to 7.0 to form a precipitate which is removed by centrifugation, and the purified mother liquor is treated by chromatography over a sulphonated polystyrene resin to recover a fraction containing lactose which is passed to the crystallization step. In an example, a whey concentrate with a solids content of 58% was crystallized, providing lactose crystals and a mother liquor containing about 27% lactose and about 13% protein by weight.
U.S. Pat. No. 4,500,549 discloses cheese flavoring agents and cheese flavor enhances in the form of enzyme-modified, lactose-hydrolyzed whey or whey fractions. The products have a flavor profile characteristic of aged cheese and a flavor intensity sufficient to serve as the sole source of cheese flavor or cheese flavor enhance in food products.
As may be seen from the above summary, the problem of lactose crystallization in cheeses has not been adequately addressed in the dairy arts. This is surprising in view of the long-felt need in the dairy industry to significantly increase the utilization of components, such as whey proteins, present in byproducts and side streams in the manufacture of dairy products while maintaining organoleptic and other desirable properties. The present inventors provide methods which allow high levels of lactose (i.e., supersaturated levels) but avoids the undesired effect of lactose crystallization even over prolonged storage times.